/Engine/Plugins/Media/MediaIOFramework/Source/MediaIOCore/Public/FileMediaCapture.h
Callback when the buffer was successfully copied to CPU ram. The callback in called from a critical point. If you intend to process the buffer, do so in another thread. The buffer is only valid for the duration of the callback.
virtual void OnFrameCaptured_RenderingThread ( const [FCaptureBaseData](API\Plugins\MediaIOCore\UMediaCapture\FCaptureBaseData) & InBaseData, [TSharedPtr](API\Runtime\Core\Templates\TSharedPtr)< [FMediaCaptureUserData](API\Plugins\MediaIOCore\FMediaCaptureUserData), ESPMode::ThreadSafe > InUserData, void * InBuffer, int32 Width, int32 Height, int32 BytesPerRow )